The present invention relates to a radiant ray-detector used in an apparatus for radiation therapy and radiological diagnosis such as X-ray computed tomography unit (X-ray CT unit) and positron computed tomography unit (positron CT unit) and radiation-determining machinery and tools for high energy-physical studies as well as a method for producing the radiant ray-detector.
One of the known radiant ray-detectors comprises a photomultiplier tube and a scintillator connected to the photomultiplier tube. When radiant rays are incident into the detector, the scintillator emits light rays and the photomultiplier tube converts the emitted light rays into electric signals for the amplification thereof. The scintillator capable of emitting light rays makes use of Bi.sub.4 Ge.sub.3 O.sub.12 crystal (hereunder referred to as "BGO crystal").
The detection of radiant rays sometimes requires the analysis of a point into which the radiation is incident (hereunder referred to as "radiant ray-incident point"). In such case, a specific radiant ray-detector is used, which comprises a plurality of photomultiplier tubes and a plurality of scintillator chips or scintillator blocks (several chips or blocks each for each entrance window of the photomultiplier tube). Japanese Patent Provisional Publication No. 4-290984 discloses a joined body of scintillator blocks for fitting to the entrance window of a radiant ray-detector capable of analyzing the radiant ray-incident points. More specifically, the reflectivities of interfaces between every neighboring two blocks differ from one another or each scintillator block is separated from the neighboring block(s) by a filler such as a BaSO.sub.4 powder or a reflecting material such as a TELFON (a fluorocarbon) tape.
The device as disclosed in the foregoing patent suffers from problems in that when radiant rays are incident upon a scintillator chip and converted into light rays, the quantity of the light transferred to the neighboring chips should be evaluated, but the quantity cannot accurately be determined through the detection of the reflectivity.